Lens processing device, lens processing method, and lens measuring method

ABSTRACT

A lens machining apparatus is provided that can execute everything required in machining eyeglass lenses, from measurement to various kinds of machining, and still can ensure high-precision machining. 
     A lens holding unit  12  which holds a lens  1  and causes the same to turn, a cutter  131  which cuts (edges) the circumferential surface of the lens in a prescribed cross-sectional shape, an end mill  141  which machines a groove in the circumferential surface of the lens whose circumferential surface has been cut (edged) and chamfers edges at the lens circumferential surface, and a lens measurement unit  15  which measures the shape and the position of the lens held by the lens holding unit are comprised.

TECHNICAL FIELD

This invention relates to a lens machining apparatus and lens machiningmethod which machines the circumferential edges of lenses being machinedto prescribed shapes for the purpose of inserting eyeglass lenses orother lenses being machined into lens frames.

BACKGROUND ART

For this type of lens machining apparatus, conventionally, a grindstonetype lens machining apparatus has been used wherewith the lenscircumferential edge is machined into the prescribed shape by grinding(edging) the circumferential surface of the lens with a grindstone.Insofar as plastic lenses are concerned, however, it is possible to dothis by edging and machining. More recently, therefore, edging (cutting)type lens machining apparatuses have been developed wherewith the lenscircumferential surface is edged (cut) with a cutter. This type ofedging lens machining apparatus is disclosed in Japanese PatentApplication Laid-Open No. H9-309051/1997 (published) and Japanese PatentApplication Laid-Open No. H11-028650/1999 (published), for example. InJapanese Patent Application Laid-Open No. H4-315563/1992 (published) andJapanese Patent Application Laid-Open No. H5-4156/1993 (published),moreover, technology is disclosed for setting and altering the grinding(edging) load on the grindstone according to the lens circumferentialedge thickness, with the object.of preventing lens cracking andefficiently performing suitable machining in cases where thecircumferential surface of a lens is ground (edged) with a grindstone(revolving machining tool for machining circumferential surfaces).andthe lens circumferential edge is machined to a prescribed shape.

However, with the edging type lens machining apparatus described inJapanese Patent Application Laid open No. H9-309051/1997 (published) andJapanese Patent Application Laid-Open No. H11-028650/1999 (published),executing the entire machining menu demanded for eyeglass lenses with asingle chuck operation in one apparatus (where a single chuck operationmeans one lens holding operation wherewith there is no movement of alens between different apparatuses) is something that still cannot bedone. More specifically, in an ordinary eyeglass lens machining menu,

(1) lens circumferential surface edging and machining (inclusive ofbevel edging)

(2) machining for forming grooves in lens circumferential surfaces, and

(3) chamfering edges where the lens circumferential surface and lensfaces intersect

are included, but it has not been possible to handle all of these menuitems with one chuck operation in one apparatus. In particular, becausehigh machining precision is demanded in bevel edging, groove machining,and chamfering, the ideal is to be able to do this with one chuckoperation, inclusive of measuring the shape and position of the lensbeing machined, but art wherewith that can be done has not beenavailable. Nor has it always been possible, merely by setting andaltering the grindstone grinding (edging) load according to the lenscircumferential thickness, as in the art described in Japanese PatentApplication Laid-Open No. H4-315563/1992 (published) and H5-4156/1993(published), to perform machining of good precision or machiningexhibiting good finished surfaces.

An object of the present invention, in view of the situation describedin the foregoing, is to provide a lens machining apparatus and lensmachining method wherewith the machining demanded for eyeglass lenses,from measurement to various machining items, can be accomplished with asingle chuck operation, and wherewith it is possible to realizehigh-precision machining.

DISCLOSURE OF THE INVENTION

A first invention is a lens machining apparatus which machines thecircumferential edge of a lens being machined for use in spectaclesaccording to shape data, comprising: a lens holding unit which holds thelens being machined at the center of the lens and rotates the held lensbeing machined about the center of the lens; a circumferential surfaceedging and machining apparatus which edges the circumferential surfaceof the lens being machined that is held in the lens holding unit to aprescribed cross-sectional shape by a revolving edging tool; a groovemachining apparatus which machines a groove in the circumferentialsurface of the lens being machined that is being held in the lensholding unit and that has been subjected to circumferential surfaceedging by the circumferential surface edging and machining apparatus; achamfering apparatus which chamfers the edges where the circumferentialsurface and lens faces intersect in the lens being machined that isbeing held in the lens holding unit and that has been subjected tocircumferential surface edging by the circumferential surface edging andmachining apparatus; and a lens shape measurement apparatus whichmeasures the lens surface shape and the lens surface position of thelens being machined being held in the lens holding unit.

With this apparatus, for the lens being machined held in the lensholding unit, lens circumference surface edging and machining can berendered by the circumferential surface edging and machining apparatus,a groove can be machined in the circumferential surface of the lens bythe groove machining apparatus, and the circumferential surface edges ofthe lens can be chamfered by the chamfering apparatus. Not only so, butthe lens surface shape and lens surface position of the lens beingmachined held by the lens holding unit in the same manner can bemeasured by the lens shape measurement apparatus. Accordingly, bymeasuring the lens shape and position with the lens being machined stillheld with the same chuck, when bevel edging is required, bevels can beformed with good precision by circumferential surface edging, and whengroove machining is required, a groove can be formed in the lenscircumferential surface with good precision. Furthermore, in cases wherechamfering is performed also, chamfered bevels can be formed with goodprecision in lens circumferential surface edges based on the measurementdata and the machining particulars.

When provision is made for edging and machining the circumferentialsurface of a lens with a revolving edging tool, as in the presentinvention, furthermore, as compared to edging with a grindstone, theamount of edging in can be freely set, wherefore the process up to andincluding the finished shape can be freely controlled. For example, goalsettings can be freely implemented, such as setting how many times torotate the lens in performing everything up to finishing, or setting thenumber of seconds in which the machining is to be concluded.

A second invention is the first invention, comprising a machining actionmechanism wherein the circumferential surface edging and machiningapparatus, the groove machining apparatus, and the chamfering apparatusare deployed fixedly, which subjects the held lens being machined tomachining actions by moving the lens holding unit relative to thosemachining apparatuses.

With this apparatus, the machining apparatuses are caused to performmachining actions by moving the lens being machined itself relative tothe tools of the machining apparatuses. Accordingly, the machiningapparatuses themselves need do nothing more than turn the tools, and theapparatus configuration is made simple.

A third invention is either the first or the second invention, wherein:the circumferential surface edging and machining apparatus and thegroove machining apparatus are deployed adjacently on a base; the axisof the revolving tool of the groove machining apparatus is deployed in adirection perpendicular to the lens holding shaft of the lens holdingunit and oriented in a direction parallel to the base; and the axis ofthe revolving tool of the groove machining apparatus, the axis of therevolving edging tool of the circumferential surface edging andmachining apparatus, and the axis of the lens holding shaft are deployedat the same height.

With this apparatus, not only are the circumferential surface edging andmachining apparatus and the groove machining apparatus deployedadjacently, but the axes thereof are aligned at the height of the axisof the lens holding shaft, wherefore a compact machining apparatus canbe realized.

A fourth invention is any of the first to third inventions, wherein: thelens holding unit comprises a lens holding shaft and a lens pressingshaft; a lens holder receptacle which mounts the lens being machined isprovided at the forward end of the lens holding shaft; the lens pressingshaft itself is deployed coaxially with the lens holding shaft, attachedso that it can slide in the lens holding shaft direction by an arm unit;the lens pressing shaft, acted on by pressure from an air cylinder,moves to the lensholding shaft side, and presses the lens being machinedby the lens presser oft he forward end thereof to the lens holding shaftside, whereby the lens being machined is held sandwiched between thelens holding shaft and the lens pressing shaft.

With th is apparatus, air is used as the source of the drive forobtaining a lens holding force, and the lens holding force (so-calledchuck pressure) can be freely adjusted by changing the pressure settingin a regulator.

A fifth invention is any of the first to fourth inventions, wherein boththe groove machining apparatus and the chamfering apparatus areconfigured by a common ball end mill.

With this invention, groove machining and chamfering are done with anend mill of small diameter used for groove edging. Therefore, comparedto machining done with a conventional grindstone, small chamfered bevelscan be accurately finished with little interference with other places.Also, because a single end mill is used for both groove edging andchamfering, the number of tools can be decreased, which contributes tocost reduction. Also, because groove edging and chamfering machining canbe done in more or less immediate succession with a single chuckoperation, machining time can be reduced. Furthermore, because a singledrive system suffices due to the employment of one tool for differentuses, the apparatus can be made smaller and costs reduced. And, becausethe number of tools is not increased, tool management is also made easy.

A sixth invention is a lens machining method wherein: a lens beingmachined for use in spectacles is held at the center of the lens, thecircumferential surface of the held lens being machined is edged by arevolving machining tool for circumferential surface machining, thecircumferential surface is edged about the entire circumference of thelens being machined by causing the lens being machined to revolve aboutthe center of the lens, and a lens having a prescribed circumferentialedge shape is thereby machined; the lens being machined is held by alens holding unit; and lens circumferential surface edging and machininginclusive of bevel edging, machining to edge a groove in the lenscircumferential surface, and chamfering the edges where the lenscircumferential surface and the lens faces intersect are performed withthe holding condition implemented by the lens holding unit maintained asit is.

This is a method that executes the entire machining menu demanded foreyeglass lenses with a single chuck operation in one apparatus (where asingle chuck operation means one lens holding operation wherewith thereis no movement of the lens between different apparatuses). In otherwords, machining wherein particularly high machining precision isrequired, such as bevel edging, groove edging, and chamfering, isperformed with a single chuck operation, so that it is possible to dosuch machining with higher precision than in the conventional case whereit is necessary to recheck the work for every machining process.

A seventh and an eighth invention are lens machining methods wherein: alens being machined for use in spectacles is held at the center of thelens, the circumferential surface of the held lens being machined isedged by a revolving machining tool for circumferential surfacemachining, the circumferential surface is edged about the entirecircumference of the lens being machined by causing the lens beingmachined to revolve about the center of the lens, and a lens having aprescribed circumferential edge shape is thereby machined; and at leastone or other of the turning speed of the revolving machining tool forcircumferential surface edging, the turning speed of the lens beingmachined when it is revolving, and the number of revolutions of the lensbeing machined for edging away a prescribed amount of material is setand altered according to either the material type or the lenscircumferential edge thickness of the lens being machined.

In some cases the revolving machining tool for the circumferentialsurface machining is a cutter for performing edging with a cutting bladeprovided at the outer periphery of the circumferential surface of thelens being machined.

In the case of a plastic lens, for example, there are both softmaterials and hard materials. And in the case of an eyeglass lens, thelens circumferential edge thickness (edge thickness) differs accordingto the power. When such is machined under uniform machining conditions,the machining load will naturally be different depending on the hardnessof the material and the lens circumferential edge thickness. Therefore,not only will the machining precision vary according to machining loaddifferences, but there is a possibility that machining efficiency willalso be affected. That being so, in the seventh to ninth inventions,provision is made for setting and altering the machining conditionsaccording to the material and the lens circumferential edge thickness.

The machining conditions in such cases include the turning speed of thecutter, grindstone, or other revolving machining tool forcircumferential surface edging, the turning speed when the lens beingmachined is revolving, and the number of revolutions in the lens beingmachined for edging away a prescribed amount of material. By setting andaltering at least one of these parameters, the machining conditions canbe made more appropriate.

In the case of an eyeglass lens, for example, as the final finishedshape is approached, the lens circumferential edge shape will cease tobe circular, wherefore the moving radial (radius) from the center ofturning to the machining point (that is, the point where the tool ismade to interfere with the lens and actually edge away the lens) willvary according to the turning angle of the lens being machined.Thereupon, the angular velocity of the lens when turning is controlledto make the circumferential speed of the machining point caused by thelens turning to be uniform. By so doing, the speed of movement of thelens (that is, the speed of movement of the machining point) relative tothe tool will become the same, and the entire circumference can bemachined under more or less the same conditions.

Furthermore, by varying the turning speed of the revolving machiningtool itself according to the movement of the machining point, withoutvarying the lens turning angle speed, the entire circumference can bemachined under more or less the same conditions.

A tenth invention is a lens machining method wherein: a lens beingmachined is caused to revolve about the center of the lens whileapplying a revolving groove tool to the circumferential surface of thelens being machined that has been machined to a prescribedcircumferential edge shape, whereby a groove is formed in thecircumferential surface of the lens being machined; and at least one orother of the turning speed of the revolving groove tool and the turningspeed when the lens being machined is revolving is set and alteredaccording to the material of the lens being machined.

An 11th invention is a lens machining method wherein: a lens beingmachined is caused to revolve about the center of the lens whileapplying a revolving chamfering tool to the edges where the lens facesand the circumferential surface of the lens being machined that has beenmachined to a prescribed circumferential edge shape intersect, wherebythe edges are chamfered; and at least one or other of the turning speedof the chamfering tool and the turning speed when the lens beingmachined is revolving is set and altered according to the material ofthe lens being machined.

Groove edging and chamfering are not machining processes which edge awaya large amount of material, wherefore the machining may be completed bycausing the lens to revolve only one time. That being so, although thenumber of lens revolutions was added as a settable and alterableparameter for the case of circumferential surface machining, here thatfactor is removed from the parameters. Furthermore, because neithergroove edging nor chamfering is a machining item wherein the machiningload is influenced by differences in the lens circumferential edgethickness, lens circumferential edge thickness is also eliminated fromthe machining conditions. Thereupon, only the material of the lens beingmachined is left as a condition, and, in terms of parameters, provisionis made for setting and altering the turning speed of the revolvinggroove tool or chamfering tool, and the turning speed when the lensbeing machined is revolving.

Thus, by setting and altering at least one of two parameters, accordingto the material of the lens being machined, the machining conditions canbe made more appropriate.

A 12th invention is a lens machining method wherein: a lens beingmachined is held by the center of the lens, the circumferential surfaceof the held lens being machined is edged away by a revolving machiningtool for circumferential surface machining, and the lens being machinedis caused to revolve about the center of the lens, whereby thecircumferential surface is edged away about the entire circumference ofthe lens being machined, and the lens is thereby machined to aprescribed circumferential edge shape; and at least one or other of theturning speed of the revolving machining tool for edging thecircumferential surface or the turning speed when the lens beingmachined is revolving is set and altered, when roughly machining thecircumferential surface of the lens being machined, and when thereafterperforming finishing machining.

A 13th invention is the 12th invention, wherein a cutter that edges thecircumferential surface of the lens being machined with a cutting bladedeployed at the outer circumference thereof is used as the revolvingmachining tool for circumferential surface machining.

A 14th invention is the 13th invention, wherein both rough machining andfinishing machining are done with the same cutter.

Rough machining, in general, is the process of removing edging materialup to the point where finishing machining is performed. Therefore, thereis no need to elicit dimensional precision or finished surfaceprecision, and it is better if the prescribed amount of edging materialcan be removed quickly. Thereupon, such is implemented by raising thefeed speed (the turning speed wherewith the lens revolves) and/orsetting the depth of edging to make it deeper. Here, in order to deepenthe edging depth, the edging load may be made large in the case ofedging with a grindstone, or the feed speed in the edging depthdirection may be set higher in the case of edging with a cutter.Finishing machining, on the other hand, is a process where dimensionalprecision and finished surface precision are elicited, wherefore raisingthe turning speed of the grindstone or cutter or other revolvingmachining tool and/or lowering the feed speed is commonly practiced.

When such is done, in the case of circumferential surface edging with acutter, both rough machining and finishing machining can be performed bychanging the turning speed of the cutter.

A 15th invention is a lens measurement method wherein: in machining thecircumferential edge of an eyeglass lens being machined according tolens frame shape data, a stylus is caused to make a trace on the lensface of the lens being machined that is held by a lens holding unit,according to the lens frame shape data, and the displacement of thatstylus in the lens thickness dimension is detected, whereby the positionon the lens face is measured; and positions on the lens face at pointsremoved from the traced points are calculated using measurement data forthe points traced by the stylus and lens design data inclusive of lensface information for the lens being machined previously given.

In the 15th invention, the lens design data includes complete coordinatedata (lens face information) relating to the lens faces. Accordingly, ifthe stylus is made to trace the lens face according to the lens frameshape data in the condition wherein the lens is held and the position onthe lens face is actually measured, based on that actually measured dataand on separately given lens design data, positional data for anyposition on the lens face can be calculated. Accordingly, when beveledging is being done, for example, by using computations to calculatepositional data for the edges on both sides of the base of the bevel,and performing the bevel edging based on those data, the position of thebevel can be finished with good precision.

A 16th invention is the 15th invention, wherein the points removed awayfrom the traced points are made the edges where the lens circumferentialsurface and the lens faces of the lens being machined intersect aftercircumferential surface finishing machining.

In the case of the 16th invention, because the points where thepositions on the lens faces are sought are made the edges where the lenscircumferential surface and the lens faces of the lens being machinedintersect after circumferential surface finishing machining, in the caseof bevel edging, for example, when the lens circumferential surface isgroove machined, or when chamfering the edge, those can be finished withgood precision.

A 17th invention is the 16th invention, wherein: the stylus is caused totrace the lens face at positions on an extended line in the direction ofthe lens holding shaft at the bevel apex when bevel edging the lenscircumferential surface; and the points removed away from the tracedpoints are made the edges at the intersections of the lens faces and thelens circumferential surface corresponding to the base of the bevel.

With the 17th invention, when doing bevel edging, positional data areacquired for the edges at the intersections of the lens faces and thelens circumferential surface corresponding to the base of the bevel,wherefore the position of the bevel can be finished with good precisionbased on the data for the edges at those intersections.

An 18th invention is any one of the 15th to 17th inventions, wherein apair of styluses is used, and positions on the front and back lens facesare measured simultaneously by causing the front and back lens faces ofthe lens being machined to be traced.

With the 18th invention, because positions on the front and back lensfaces are measured simultaneously with the pair of styluses, the edgethickness can be calculated from those data.

A 19th invention is a lens machining method wherein: a lens measurementmethod cited in any one of inventions 15 to 18 cited above is used; dataon positions on the lens faces of the lens being machined are acquired;and the lens being machined is subjected to circumferential surfacemachining based on those data.

With the 19th invention, lens circumferential surface machining isperformed on the bases of data acquired by a measurement methoddescribed earlier, wherefore the circumferential surface machiningprecision can be raised.

A 20th invention is the 19th invention, wherein a bevel is formed in thelens circumferential surface when performing the circumferential surfacemachining.

With the 20th invention, a bevel is formed on the circumferentialsurface of the lens on the basis of data acquired by a measurementmethod described earlier, wherefore the position of the bevel can befinished with good precision.

A 21st invention is the 19th invention, wherein, after thecircumferential surface machining, a groove is machined in thecircumferential surface using the acquired data.

With the 21st invention, a groove is formed in the circumferentialsurface of the lens on the basis of data acquired by a measurementmethod described earlier, wherefore the position of the groove can befinished with good precision.

A 22nd invention is any one of the 19th to 21st inventions, wherein,after the circumferential surface machining, the edges where the lensfaces and the lens circumferential surface intersect are chamfered usingthe acquired data.

With the 22nd invention, the edges where the lens faces and the lenscircumferential surface intersect are chamfered on the basis of dataacquired by a measurement methods described earlier, wherefore thechamfered bevels can be finished with good precision.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view representing the overall configuration of alens machining apparatus in an embodiment of the present invention;

FIG. 2 is a plan representing the overall configuration of a lensmachining apparatus in an embodiment of the present invention;

FIG. 3 is a front elevation representing the configuration of a lensmachining apparatus in an embodiment of the present invention;

FIG. 4 is a plan representing the detailed configuration of a lensholding unit in a lens machining apparatus in an embodiment of thepresent invention;

FIG. 5(a) is a plan representing the detailed configuration of a cutting(edging) action mechanism in a lens machining apparatus in an embodimentof the present invention, while FIG. 5(b) is a view from the Vb—Vbarrows in FIG. 5(a);

FIG. 6 is a side elevation of a measurement unit in a lens machiningapparatus in an embodiment of the present invention, showing thecondition thereof with a measurement head in an unloaded position at (a)and the condition with the measurement head loaded at (b);

FIG. 7 is a plan of a measurement unit in a lens machining apparatus inan embodiment of the present invention, showing the condition thereofwith a measurement head in an unloaded position at (a) and the conditionwith the measurement head loaded at (b);

FIG. 8 is a front elevation of a measurement unit in a lens machiningapparatus in an embodiment of the present invention;

FIG. 9(a) is a theoretical configuration diagram of a measurement headin a lens machining apparatus in an embodiment of the present invention,FIG. 9(b) is a side elevation representing the details of the forwardend of a stylus, and FIG. 9(c) is a front elevation of the same;

FIG. 10 is a plan representing a condition wherein the stylus of ameasurement head is loaded on a lens in a lens machining apparatus in anembodiment of the present invention;

FIG. 11 is a side elevation representing a condition wherein the stylusof a measurement head is loaded on a lens in a lens machining apparatusin an embodiment of the present invention;

FIG. 12 is an explanatory diagram for shape data;

FIG. 13 represents the configuration of the cutter of a cutter turningmechanism in a lens machining apparatus in an embodiment of the presentinvention, with a semi-sectional view given at (a), a side elevation at(b), and an enlarged diagram of the main parts of a bevel cutter at (c);

FIG. 14 is a side elevation representing the condition wherein a lens isbeing machined with the cutter of a cutter turning mechanism in a lensmachining apparatus in an embodiment of the present invention;

FIG. 15 is a plan representing the condition wherein a lens is beingmachined with the bevel cutter of a cutter turning mechanism in a lensmachining apparatus in an embodiment of the present invention;

FIG. 16 is a plan representing a condition wherein an edge in a lensedge surface is being chamfered and a condition wherein a groove isbeing cut (edged) in a lens edge surface by an end mill in an end millturning mechanism in a lens machining apparatus in an embodiment of thepresent invention;

FIG. 17 is a side elevation representing a condition wherein groovecutting (edging) or chamfering is being performed by an end mill in alens machining apparatus in an embodiment of the present invention;

FIG. 18(a) is an enlarged diagram used in describing cases of performinggroove cutting (edging) and chamfering with an end mill in a lensmachining apparatus in an embodiment of the present invention, whileFIG. 18(b) is an explanatory diagram for chamfering when there is abevel;

FIG. 19 is an explanatory diagram for a lens holder in a lens machiningapparatus in an embodiment of the present invention, with a sideelevation of the lens holder given at (a), a plan of the lens holdingsurface of the lens holder at (b), a cross-sectional view of minuteundulations formed in the lensholding surface at (c), a cross-sectionalview representing a condition wherein a pad is pressed onto those minuteundulations at (d), a cross-sectional view of minute undulations formedin the lens holding surface of a conventional lens holder at (e), and across-sectional view representing a condition wherein a pad is pressedonto those minute undulations at (f);

FIG. 20 is a diagram of how a lens 1 is held by a lens holder 19;

FIG. 21 is a cross-sectional view used in explaining the degree ofadhesion based on the relationship between the curvature of a lens and alens holder in a lens machining apparatus in an embodiment of thepresent invention;

FIG. 22 is a simplified block diagram of the electrical configuration ofa lens machining apparatus in an embodiment of the present invention;

FIG. 23 is a flowchart for machining processes performed by a lensmachining apparatus in an embodiment of the present invention;

FIG. 24 is a table giving actual examples of parameters determinedaccording to different types of machining processes (where cutterturning speed=tool turning speed, and lens holding shaft turningspeed=feed speed);

FIG. 25 is a graph plotting the relationship between the maximummaterial thickness of a lens and the number of cutting (edging)revolutions (number of machining revolutions), in terms ofexperimentally determined results, in a case where machining of aprescribed precision is possible without shaft displacement or the like;

FIG. 26 is an explanatory diagram for a method of correcting lensmeasurements performed with a lens machining apparatus in an embodimentof the present invention;

FIG. 27(a) is a diagram of machining processes that can be selected witha lens machining apparatus in an embodiment of the present invention,while FIG. 27(b) is a flowchart therefor; and

FIG. 28 is an explanatory diagram for the machining processing indicatedin FIG. 23(b), with a front elevation of a lens given at (a) and across-sectional view of a lens given at (b).

1 . . . lens, 12 . . . lens holding unit, 121 . . . lens holding shaft,121 a . . . lens holder receptacle, 122 . . . lens pressing shaft, 122 a. . . lens presser, 123 . . . air cylinder, 13 . . . cutter turningmechanism (circumferential surface edging apparatus), 131 . . . cutter(revolving edging tool), 14 . . . end mill turning mechanism (groovemachining apparatus, chamfering apparatus), 141 . . . end mill(revolving tool), 15 . . . measurement unit, 16 . . . measurement head,161, 162 . . . styluses, 19 . . . lens holder, 992 . . . air jet nozzle(air jetting apparatus), 993 . . . cleaning port (suction removaldevice).

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a perspective view of the overall configuration of a lensmachining apparatus in an embodiment; FIG. 2 is a plan view of thatoverall configuration; and FIG. 3 is a front view of that overallconfiguration as seen from the front side of the apparatus. A lensmachining apparatus and lens machining method pertaining to anembodiment of the present invention are described below whilereferencing these drawings. The lens machining apparatus relating tothis embodiment, moreover, is not a grinding (edging) type that grinds(edges) a lens circumferential surface with a grindstone, as has beencommon conventionally, but rather a cutting (edging) type machiningapparatus that forcibly cuts (edges) a lens circumferential surface witha revolving cutting (edging) tool. This type of cutting (edging) lensmachining apparatus is particularly effective for plastic lenses, andmachining efficiency can be enhanced therewith.

In these drawings, a machining apparatus 10 is configured by theattachment of several mechanisms to a base 11. The base plate 11 a ofthe base 11 is deployed horizontally. On that base plate 11 a aredeployed a lens holding unit 12, a cutter turning mechanism 13 forperforming lens circumferential surface cutting (edging), and an endmill turning mechanism 14 for performing groove machining andchamfering. These mechanisms are laid out on the base plate 11 a in moreor less the same plane, with the cutter turning mechanism 13 and the endmill turning mechanism 14 both deployed on the front side of theapparatus and the lens holding unit 12 deployed more to the back side ofthe apparatus.

A measurement unit 15 is also deployed on the base plate 11 a. Themeasurement unit 15 has a measurement head 16 that is a lens shapemeasuring device. This measurement head 16 is deployed in the open spaceabove the cutter turning mechanism 13 and the end mill turning mechanism14 in order to avoid interference with the cutter turning mechanism 13and the end mill turning mechanism 14.

The lens holding unit 12, while holding a lens being machined 1, alsocauses the lens being machined 1 to revolve about the center of the lensin order to move the machining position in the circumferential directionof the lens. The cutter turning mechanism 13 has a cutter (revolvingedging tool) 131 for forcibly cutting (edging) the circumferential edgeof the lens being machined 1, and performs flat cutting (edging) andbevel cutting (edging) on the circumferential surface of the lens beingmachined 1 by causing the cutter 131 to revolve horizontally about ashaft. The end mill turning mechanism 14 has a ball end mill 141(hereinafter simply “end mill”) as a machining tool and, by causing thatend mill 141 to revolve about a horizontal shaft, forms grooves in thecircumferential surface of the lens 1 (these grooves are for passing athread of nylon or the like when mounting the lenses in a rimlessframe), and chamfers the edges where the lens faces and thecircumferential surface of the lens being machined 1 intersect. Themeasurement unit 15 has a measurement head 16 for measuring the edgethickness of the lens 1 and the lens position in the direction of edgethickness, and is capable of turning the measurement head 16 in up anddown directions as necessary.

The lens holding unit 12 is deployed so that it can, by a mechanism tobe described below, slide in a direction parallel to the plane of thebase plate 11 a and perpendicular to the shaft of the cutter 131 (thatdirection hereinafter called the Y axis direction), and so that it canslide in a direction parallel to the plane of the base plate 11 a andparallel to the shaft of the cutter 131 (that direction hereinaftercalled the Z axis direction).

The cutter turning mechanism 13 is fixed on the base plate 11 a. Thecutter 131 of the cutter turning mechanism 13 is attached to a spindle132, and, by transmitting the turning of a cutter turning motor 133 by abelt 134 to the spindle 132, it is caused to revolve about its own shaftcenterline.

On the base plate 11 a is deployed a cutting-in action mechanism 24.This cutting-in action mechanism 24 (which is equivalent to a machiningaction mechanism) is a mechanism that moves the lens holding unit 12 inthe Y axis direction and subjects the lens 1 to a cutting-in action onthe cutter 131 or end mill 141.

On the lower side of the base plate 11 a is deployed a duct (not shown)configuring an apparatus for sucking out the machining dust. This ductis connected to a cleaning port 993 opened in the base plate 11 a. Abovethis cleaning port 993 is deployed a plurality of air jet nozzles 992comprising an air jetting apparatus. These air jet nozzles 992 aredeployed in the vicinity of the cutter 131 and the end mill 141 so thatthe machining dust is blown by the air jet nozzles 992 whencircumferential surface cutting (edging), groove cutting (edging), orchamfering machining operations are being performed on the lens beingmachined 1 loaded in the lens holding unit 12, and so that the blownmachining dust is sucked in and removed from the cleaning port 993.

The mechanisms of the lens machining apparatus 10 are electricallycontrolled by control devices (not shown), which are describedsubsequently, deployed below the base plate 11 a, for example.

On the base plate 11 a of the base 11 is deployed a Y table 20 thatmoves in the Y axis direction. This Y table 20 is deployed so that itcan slide on two parallel rails 21 and 21 that are fixed to the baseplate 11 a so as to be oriented in the Y axis direction. The Y table 20is also linked to the cutting-in action mechanism 24, described above,and is controlled by the cutting-in action mechanism 24 so that it movesin the Y axis direction.

On the upper surface of the Y table 20 are fixed two rails 31 and 31 soas to be oriented in the Z axis direction. On these rails 31 and 31 isdeployed a Z table 30 slidably. The Z table 30 is controlled so that itmoves by a Z table movement mechanism 33 (an axial direction movementmechanism that moves the lens in that axial direction) that is fixed onthe Y table 20. The Z table movement mechanism 33 is provided with a Zaxis motor 331. To the turning shaft of the Z axis motor 331 is linked aball screw 332. A slide block 333 secured to the Z table 30 is screwedonto the ball screw 332. The Z axis motor 331 can move in both theforward and reverse directions according to instructions from a controldevice described subsequently.

By the turning of the Z axis motor 331, the ball screw 332 also turns.When the ball screw 332 turns, the slide block 333 is moved, and the Ztable 30 that is made moves, integrally with the slide block 333, alongthe rails 31 and 31. On the upper surface of the Z table 30 is fixed thelens holding unit 12.

FIG. 4 is a plan view showing the detailed configuration of the lensholding unit 12.

The lens holding unit 12 has a lens holding shaft 121 that is parallelto the shaft of the cutter 131 (cf. FIG. 2). The lens holding shaft 121is made to turn by a turning mechanism inside the lens holding unit 12.At the forward end of the lens holding shaft 121 is fixed a lens holderreceptacle 121 a. A lens holder 19 to which the lens being machined 1 issecured is attached to the lens holder receptacle 121 a so that it canbe freely detached.

To the lens holding unit 12 is attached a lens pressing shaft 122 (whichis also called a lens holding shaft), coaxially with the lens holdingshaft 121, capable of sliding in the direction of the lens holding shaft121 by an arm 122 b. The lens pressing shaft 122 moves toward the lens1, acted on by air pressure from an air cylinder 123, presses againstthe lens 1 with a lens presser 122 a, and thus holds the lens 1 betweenitself and the lens holding shaft 121.

In this case, to the end surface (formed in a concave shape) of the lensholder 19, the convex side lens face 1A of the lens 1 is bonded, with anintervening double-sided adhesive pad 191, and the lens presser 122 apresses against the concave side lens face 1B of the lens 1. The lenspresser 122 a is attached to the forward end of the lens pressing shaft122 so that it can be tilted in any direction, made so that it pressesagainst the concave side lens face 1B of the lens 1 in a balanced mannerwithout striking on only one side.

The air cylinder 123 provided inside the case 12 a of the lens holdingunit 12 causes the rod 123 a thereof to move in the Z axis direction bythe pressure of air sent from an air pump (not shown) providedexternally. To the forward end of the rod 123 a is secured an arm 123 b,deployed so that it moves integrally with the rod 123 a. To the arm 123b are secured a guide table 123 c and the arm 122 b of the lens pressingshaft 122. The lens pressing shaft 122 is deployed so that it can movealong a long hole 12 b that is formed in the case 12 a so as to extendin the Z axis direction. At the forward end of the lens pressing shaft122, the lens presser 122 a is deployed so that it can turn freelyforwards or backwards about the Z axis.

The guide table 123 c is fit, so that it can slide, onto a rail 124 a,deployed on a side surface of a rail platform 124 so that it is parallelto the Z axis direction. As a consequence, when the rod 123 a of the aircylinder 123 moves, the arm 123 b, guide table 123 c, and lens pressingshaft 122 move in the Z axis direction integrally therewith, and thelens presser 122 a presses against or separates from the lens 1.

A lens turning motor 125 is deployed inside the case 12 a. To the shaft125 a of this lens turning motor 125 is linked a small-diameter gear 125c through a coupling 125 b. The gear 125 c is linked to a large-diametergear 125 d. And to the gear 125 d is provided a pulley 125 e. Thispulley 125 e is linked by a belt 125 f to a pulley 121 b fixed on theshaft 121.

Thus, when the lens turning motor 125 is driven, the turning of theshaft 125 a is transmitted to the coupling 125 b and the gear 125 c, andis speed-reduced by the gear 125 d. This speed-reduced turning istransmitted by the pulley 125 e, belt 125 f, and pulley 121 b to thelens holding shaft 121, whereupon the lens 1 turns.

To the lens holding shaft 121 is secured a slit plate 121 c. The turningposition of this slit plate 121 c is detected by a light sensor 126fixed inside the case 12 a, and thereby the position of the point oforigin of the lens 1 held by the lens holding shaft 121 is detected.

With the lens holding unit 12 configured in this way, when the lens 1 issecured to the lens holder receptacle 121 a, the air cylinder 123 drivesand the lens pressing shaft 122 moves toward the right in the drawing.Thereupon, the lens 1 is secured by the pressing of the lens presser 122a on the lens 1. When the lens 1 is being machined and when lensmeasurements are being made, the lens turning motor 125 drives, the lensholding shaft 121 turns, and the lens 1 is turned thereby. Also, by theturning of the lens 1, the lens presser 122 a also turns integrallytherewith.

FIG. 5(a) is a plan that in simplified form represents the configurationof the cutting-in action mechanism 24 as a Y-axis-direction movementmechanism, while FIG. 5(b) is a view from the Vb—Vb arrows in FIG. 5(a).The cutting-in action mechanism 24 is secured to the upper surface of aconcave part in a concave member 68 that is attached to the lowersurface at an opening in the base plate 11 a. On the upper surface ofthe concave part of the concave member 68 are deployed two bearingsupport members 61 and 61, at an interval. To these support members 61and 61 is attached a bore screw 62 oriented in the Y axis direction sothat it can turn freely. One end of the bore screw 62 is linked to theshaft of a cutting-in motor 63 that is secured to the concave member 68.

The cutting-in motor 63 turns in both the forward and reversedirections, according to instructions from a control device to bedescribed subsequently, and the bore screw 62 turns in linkage with theturning of this cutting-in motor 63. A moving block 64 is screwed ontothe bore screw 62, and the moving block 64 is linked to the Y table 20described earlier. Thus the Y table 20 and the lens holding unit 12 movein the Y axis direction, integrally with the moving block 64 in thecutting-in action mechanism 24. Thus cutting-in operations are performedby the lens 1 against the cutter 131.

To the moving block 64 is attached a switch piece 641. This switch piece641 turns on a light sensor 642 secured to the concave member 68 whenthe moving block 64 is in a point of origin position that constitutes areference for cutting-in amount measurement. When the moving block 64 isat one of the limiting positions, a light sensor 643 secured to theconcave member 68 turns on. And when the moving block 64 is at the otherlimiting position, a light sensor 644 secured to the concave member 68turns on.

Next, the end mill turning mechanism 14 is described. The end millturning mechanism 14 is deployed adjacent to the cutter 131 of thecutter turning mechanism 13, secured to the top of the base plate 11 a,oriented in a direction so that the axis of the end mill 141 isperpendicular both to the lens holding shaft 121 and the lens pressingshaft 122 of the lens holding unit 12, and parallel to the base plate 11a. Furthermore, the axis of the end mill 141, the axis of the cutter131, the lens holding shaft 121, and the lens pressing shaft 122 arepositioned at the same height. The end mill turning mechanism 14 isprovided with a spindle motor 142 that drives the end mill 141 so thatit turns.

Next, the measurement unit 15 is described with reference to FIGS. 6 to8.

The measurement unit 15 has a measurement head 16 that is provided witha pair of styluses 161 and 162. As diagrammed in FIG. 8, the measurementhead 16 is attached by a turning shaft 152 to two supporting walls 151and 151 erected at an interval on the base plate 11 a. The turning shaft152 is deployed so as to be parallel with the shaft of the cutter 131,supported so that it can turn in the up and down directions at a heightnear the upper ends of the supporting walls 151 and 151. To the turningshaft 152 are secured two arms 163 and 163 that project downward fromthe measurement head 16. Provision is thereby made so that, by turningthe turning shaft 152, the measurement head 16 turns between an unloadedposition (holding position when not being used in measuring) asindicated in FIG. 6(a) and FIG. 7(a) and a loaded position (positionwhen being used in measuring) as diagrammed in FIG. 6(b) and FIG. 7(b).

One end of the turning shaft 152 protrudes from one of the supportingwalls 151 in the horizontal direction. This protruding end is linkedthrough a coupling 152 a to the turning shaft 155 a of an air drive typemeasurement head turning actuator 155 that is secured by a frame 154 onthe base plate 11 a. The measurement head 16 is moved to the unloadedposition and to the loaded position by the air drive type measurementhead turning actuator 155, wherefore, stoppers 156 and 157 are deployedso that the measurement head 16 definitely stops in the unloadedposition and in the loaded position (cf. FIG. 6). The stoppers 156 and157 are deployed on non-moving members, that is, on brackets 156 a and157 a secured to the supporting wall 151. The configuration is such thatthe measurement head 16 is positioned by having certain places on themeasurement head 16 strike these stoppers 156 and 157.

The stopper 156 on the unloaded position side does not need to exhibit aparticularly accurate positioning function, but the stopper 157 on theloaded position side affects the precision of measurement by themeasurement head 16, and therefore must exhibit an extremely accuratepositioning function. For that reason, a microhead ({fraction (1/1000)}mm) capable of adjusting the positioning position precisely is used forthe stopper 157 on the loaded side. By positioning with this microheadtype of stopper 157, the styluses 161 and 162 of the measurement head 16moved to the loaded position are accurately held at the same heightlevel as the turning center of the lens holding shaft 121 and theturning center of the cutter 131. The configuration is made so thatdeviations in the initial positioning can be adjusted.

When the measurement head 16 has been moved to the loaded position or tothe loaded position by the turning actuator 155, there is a danger thata shock will occur when the certain places on the measurement head 16strike the stoppers 156 and 157, wherefore, shock absorbers 158 and 159that exhibit a shock absorbing action are deployed on the arm 163 of themeasurement head 16 and on the bracket 156 a secured to the supportingwall 151. These shock absorbers 158 and 159 exhibit a shock reducingaction when they strike members on the respective sides immediatelybefore the measurement head 16 strikes the stoppers 156 and 157, therebyplaying a role to soften the impact of the measurement head 16 againstthe stoppers 156 and 157.

Also, when the measurement head 16 is moved to the loaded position, itis necessary to verify that the measurement head 16 has fallen into theloaded position, wherefore, as diagrammed in FIGS. 6 and 7, a lightsensor 160 is deployed in a bracket 160 a secured to the supporting wall151, on the loaded position side, so that the presence or absence of themeasurement head 16 there can be detected.

By being configured in this way so that it can turn between the loadedposition and the unloaded position, provision is made so that themeasurement head 16 can be delivered from above to the position wheremeasurement is to be done (the loaded position), when needed, andremoved to a holding position above (the unloaded position) when notneeded. Accordingly, by mounting the measurement head 16 in this mannerso that it does not interfere with the work done by the cutter 131 orend mill 141, once the lens 1 is held by the lens holding unit 12,everything from measurement to machining can be done without unchuckingthe lens 1, so that work can be moved along with a single chucking.Furthermore, in special cases, when effecting measurements as necessaryduring the course of machining the lens 1, the edge thickness and soforth of the lens 1 can be measured, with the lens 1 held just as it is,without releasing the chucking on the lens 1.

A concrete configuration of the measurement head 16 is described next.As diagrammed in FIG. 2 and FIG. 7(a), for example, the measurement head16 is provided with a pair of styluses (measuring probes) 161 and 162that make contact with the convex side lens face and the concave sidelens face of the lens being machined 1 that is held by the lens holdingunit 12. These two styluses 161 and 162 are positioned on a straightline parallel to the thickness dimension of the lens (in a directionparallel with the turning shaft 152), deployed so that the sphericaltips thereof are in mutual opposition.

FIG. 9(a) is a diagram that represents the theoretical configuration ofthe measurement head 16, while FIGS. 9(b) and 9(c) are diagrams thatrepresent the configuration of the tip end of the stylus 161.

The styluses 161 and 162 are attached to arms 164 and 165 that are movedin parallel by guiding mechanisms (not shown). The stylus 161 (with theother stylus 162 having the same configuration), as diagrammed in detailin FIG. 9(b) and 9(c), is structured such that a perfectly sphericalsteel ball (being a steel ball made of super hard steel of 2φ or so thatis highly resistant to wear and shape deformation) 161 b is attached tothe tip of a rod-shaped stylus trunk 161 a. A flat surface is formed onthe side surface of the stylus trunk 161 a, and the steel ball 161 b isattached eccentrically to the stylus trunk 161 a toward that flatsurface side.

In this case, one might naturally first consider attaching the steelball in the very middle of the stylus trunk. When that is done, however,there is a great danger of the steel ball being attached at a positionthat is actually shifted away from the center due to attachment error ormachining error, whereupon stylus center coordinate shift correctionbecomes difficult. Thereupon, if a flat surface is formed on a sidesurface of the stylus trunk 161 a as described earlier, and the steelball 161 b is attached so that the outer circumference of the steel ball161 b touches the extended plane of the flat surface, the position ofthe center of the steel ball 161 b will be located at a distance fromthe flat surface of the stylus trunk 161 a that is equal to the radiusthereof. Accordingly, it becomes possible to ascertain the positionalcoordinates of the center of the steel ball 161 b accurately, and thatcan be reflected in the measurements.

The arms 164 and 165 to which such styluses 161 and 162 are attachedmove in parallel, whereby the interval between them opens and closes.The arms 164 and 165 are linked to movable probes 166 b and 167 b inlinear encoders 166 and 167 inside of which are deployed springs(contracted springs in the example diagrammed) 166 a and 167 a, and areenergized in the closed condition by the springs 166 a and 167 a. Thelinear encoders 166 and 167 are devices which electrically detect themoving positions of the movable probes 166 b and 167 b, wherefore thepositions of the styluses 161 and 162 are detected by the linearencoders 166 and 167.

As described above, the styluses 161 and 162 are energized toward theclosed direction by the springs 166 a and 167 a so that theyautomatically close, and they must be moved by some driving mechanismtoward the open direction. Thereupon, a belt 173 wound about a pair ofpulleys 171 and 172 is deployed above the arms 164 and 165, the pulley171 is made to turn by a stylus opening and closing DC motor 170,causing the belt 173 to go around, and thereby the arms 164 and 165 arehooked by engagement pieces 173 a and 173 b provided on the belt 173 andcaused to move in the open direction.

Furthermore, provision is made in this case also so that it can bedetected whether the styluses 161 and 162 are opened or closed bydetecting the position of the engagement piece 173 a with opticalsensors 174 and 175. The configuration is also such that it can bedetected whether or not the arms 164 and 165 are positioned at theirpoints of origin by the optical sensors 176 and 177.

The principle wherewith lens positions are measured by the styluses 161and 162 of the measurement head 16 is diagrammed in FIGS. 10 and 11. Thestyluses 161 and 162 oppose each other on the same straight lineparallel with the lens holding shaft 121. Now, when the lens 1 is movedbetween the tips of the two styluses 161 and 162 in a condition whereinthe styluses 161 and 162 have been opened by driving the belt 173diagrammed in FIG. 9, and the belt 173 is returned to the opposite side,the styluses 161 and 162 are closed by the action of springs 166 a and167 a in the linear encoders 166 and 167, and, as diagrammed in FIG. 10,one stylus 161 brings its tip up against the convex side lens face 1A ofthe lens 1, while the other stylus 162 brings its tip up against theconcave side lens face 1B of the lens 1.

Now, when the lens 1 is controlled so as to move based on lens frameshape data (=shape data), the styluses 161 and 162 trace a locus Sfollowing the shape data, as diagrammed in FIG. 11.

FIG. 12 is an explanatory diagram for shape data. In FIG. 12, theholding center point of the lens 1 held by the lens holding unit 12 isrepresented as Oc (set here to the optical center). When this is done,any point Si on the locus S can be expressed as moving radialinformation (ρi, θi) that constitutes polar coordinates with Oc at theorigin. Here, ρi is the distance (moving radial length) from Oc to anypoint Si on the locus S, while θi is the angle (moving radial angle)subtended by the straight line OcSi with a reference line OcSo thatpasses through Oc. When shape data are given by a method such as this,by controlling the cutting-in action mechanism 24 to a quantity based onthe moving radial length ρi, the lens 1 will move in a lens radialdirection relative to the styluses 161 and 162, and the styluses 161 and162 will be positioned at a position that is removed from the centeraxis of the lens holding shaft 121 by the moving radial length ρi.Moreover, by controlling the lens turning mechanism of the lens holdingunit 12 so as to turn by an amount based on the moving radial angle θi,the lens 1 will be made to turn by precisely the moving radial angle θirelative to the styluses 161 and 162. The tips of the styluses 161 and162 trace over the convex side lens face 1A and the concave side lensface 1B of the lens 1, wherefore, by detecting the amount of movement inthe styluses 161 and 162 with the linear encoders 166 and 167, it ispossible to obtain lens position data (Zi) for the edge thicknessdimension (Z axis direction) corresponding to the moving radialinformation. And, by performing this detection operation for all of themoving radial information (ρi, θi), it is possible to obtain positiondata for the convex side lens face 1A and position data for the concaveside lens face lB (ρi, θi, Zi), on the lens moving-radial shape locus(ρi, θi). Lens thicknesses (edge thicknesses) on the lens moving radialshape locus (ρi, θi) can also be calculated from such position data forthe convex side lens face 1A and position data for the concave side lensface 1B.

The cutter 131 of the cutter turning mechanism 13 is next described.

The configuration of the cutter 131 is diagrammed in FIG. 13. Thiscutter 131, as diagrammed in FIG. 13(b), has two cutting blades 131 a ofa projecting form at the outer circumferential surface thereof. Thecutting blades 131 a are deployed at an interval of 180 degrees in thecircumferential direction. These cutting blades 131 a are configured bylaminated chips wherein fine crystalline diamond and a superhard alloyare bonded together by sintering under extremely high pressure. Thecutter 131, as diagrammed in FIG. 13(a), has three cutters aligned onthe same axis line, and linked integrally, those three cutters being asmall bevel cutter Y1 having a small bevel groove Y1 a (example: formetal frames), a large bevel cutter Y2 having a large bevel groove Y2 a(example: for plastic cellframes), and a flat-cutting (edging) cutter H1having no bevel groove (example: for rimless frames), configured so thatthe cutter parts are used in different ways depending on the machiningbeing done.

The bevel grooves Y1 a and Y2 a are as diagrammed in FIG. 13(c). Thebevel angle is 110 to 125 degrees, for example, while the bevel heightis 0.4 to 0.68 mm for the small bevel, for example, and 0.7 to 0.9 mmfor the large bevel, for example. The flat surface adjacent to the bevelgrooves Y1 a and Y2 a is tapered at an angle of 3.5 to 5 degrees, forexample. This is to create clearance for the frame adjacent to thebevel.

The principle whereby the circumferential edge of the lens 1 is cut(edged) by the cutter 131 is described in FIG. 14.

Looking from the site of interference between the cutter 131 and thelens 1, the cutter 131 turns from above to below, while the lens 1 turnsfrom below to above. Thereupon, at the site of interference, the cuttingblade 131 a of the cutter 131 forcibly cuts (edges) the lens 1 byprecisely the set cutting-in amount. Now, when a machining program isproduced on the basis of the lens frame shape data (=shape data), andthe lens 1 is controlled so as to move according to that machiningprogram, the cutter 131 cuts (edges) the circumferential surface of thelens 1 according to the particulars of the movement of the lens 1.

For flat cutting (edging), the lens 1 is positioned at a suitableposition in front of the flat-cutting (edging) cutter H1, and machiningis performed by driving the cutting-in action mechanism 24 while turningthe cutter 131. For bevel edging, as diagrammed in FIG. 15; the lens 1is positioned at a suitable position in front of the bevel cutters Y1and Y2, and machining is performed by driving the cutting-in actionmechanism 24 while causing the cutter 131 to turn, in conjunction withthe movement of the Z table movement mechanism 33 in the Z axisdirection. In FIG. 15, 1 a indicates the bevel.

The principle whereby groove cutting (edging) and chamfering the edgesat both extremities of the bevel (lens circumferential surface) are doneby the end mill 141 is diagrammed in FIG. 16, FIG. 17, FIG. 18(a) andFIG. 18(b). When cutting (edging) out a groove 1 b in the edge surface(circumferential surface) of a lens 1 that has been shape-machined, asdiagrammed in FIGS. 16 and 17, the edge surface is made to approach thetip of the revolving end mill 141 by moving the lens 1 under control.

When that approach has been completed, the cutting in amount is suitablyset by the cutting-in action mechanism 24 while causing the lens 1 toturn. When that is done, in association with the turning of the lens 1,a groove 1 b is continuously formed at a preset depth (cutting-inamount). During the machining, the distance between the position on theedge surface currently contacted by the end mill 141 and the center ofthe lens is computed, and control is effected to move the position inthe Y axis direction of the lens 1 according to that distance, based onthe shape data for the lens 1. During the machining, furthermore, thelens 1 is controlled so as to move in the Z axis direction so that,based on the shape data, the tip of the end mill 141 is alwayspositioned either at a certain position on the edge surface, such as theposition at the center of the edge surface in the width direction (edgethickness direction), or at a position removed a certain distance fromthe front surface of the lens (the convex side lens face 1A).

When the lens 1 is turned a full turn while continuing such control, thegroove 1 b is formed in the lens edge surface all around thecircumference of the lens. Upon returning to its original startingpoint, the end mill 141 moves in a direction opposite to that of theapproach and separates from the lens 1.

When performing thread chamfering to prevent cracking and chipping onthe two edges of the bevel (the edges where the lens circumferentialsurface and lens surfaces intersect), the R part of the tip of the endmill 141 is used, as diagrammed in FIG. 18. At (a) therein is diagrammedthe case where chamfering is performed after a groove 1 b has beenmachined in the lens circumferential surface, while at (b) is diagrammedthe case where chamfering is performed after a bevel la has beenmachined in the lens circumferential surface. When the edge 1 c on theconvex side or the edge 1 d on the concave side are taken off with thetip of the end mill 141, the shoulder portion of the R part of the tipof the end mill 141 is used.

At this time, using positional coordinate data for the edges 1 c and 1d, the position of the lens 1 relative to the end mill 141 is found (forchamfering). That is, the chamfer dimensions (ΔZ, ΔY) are more or lessdetermined by the shape, etc., of the edges 1 c and 1 d, wherefore, byentering the position of the center of the end mill 141 performing thechamfering, together with the radius of the R part thereof and thepositional data for the edges 1 c and 1 d, into the computation, theremoval quantities Q11, Q12, Q21, and Q22, which are positionalcorrelations between the tip of the end mill 141 and the edges 1 c and 1d of the lens 1, are determined. That being so, from the data of thecoordinates of the center of the end mill 141 and the removal quantitiesQ11, Q12, Q21, and Q22, positional coordinate data for the edges 1 cand1 d of the lens 1 to be controlled can be determined, and, by causingthe lens 1 to move around while controlling the position of the lens 1in the Y axis direction and the Z axis direction, based on thepositional coordinate data, mutual positioning of the lens 1 and the endmill 141 for effecting proper chamfering will be effected. In otherwords, by moving the lens 1 in the Y axis direction and the Z axisdirection and also causing it to make a revolving movement, the edges 1c and 1 d to be machined can be accurately positioned relative to the Rpart of the tip of the end mill 141 that is being driven so as to turnat a stationary position. This is possible because the shape andposition information for the end mill 141 and the position informationfor the lens 1 are accurately ascertained. The chamfering on the convexface side and the chamfering on the concave face side are performedindependently, inclusive of the respective approaches of the lens 1 tothe end mill 141.

FIG. 19 is a diagram representing the configuration of the lens holder19 used in this lens machining apparatus 10, while FIG. 20 is a diagramthat shows how the lens 1 is held by the lens holder 19. As diagrammedin FIG. 19(a) and FIG. 20, the lens holder 19 is a pipe-shaped devicehaving a fitting stem 193 that fits into the inner circumference of thetubular lens holder receptacle 121 a diagrammed in FIG. 4, a fittingstem flange 194 that comes up against the end surface of the lens holderreceptacle 121 a, and a lens holding flange 196 that presses against theconvex side lens face 1A of the lens 1 with an intervening double-sidedadhesive pad 191, as diagrammed in FIG. 10 and FIG. 20. In the fittingstem flange 194 is formed a turn-stopping cutout 195 that fits aprojection (not shown) on the side of the lens holder receptacle 121 a.The fitting stem 193 has, for example, a length of 35 mm, an outerdiameter of 14 mm φ or so, and a hole diameter in a center hole 7 of 10mm φ or so. The fitting stem flange 194, which defines the amountwhereby the fitting stem 193 fits into the lens holder receptacle 121 a,has a thickness of 5 mm or so and an outer diameter of 20 mm φ or so. Inthe circumferential surface of the fitting stem flange 194, moreover,the turn-stopping cutout 195 is formed as a turn-preventer forpreventing the lens holder 19 from turning relative to the lens holderreceptacle 121 a. In the part of this turn-stopping cutout 195 that isopen on the side opposite that of the lens holding flange 196, a taperedsurface 195 a that opens toward the outside is formed in order tofacilitate fitting to the lens holder receptacle 121 a.

The lens holding flange 196 is deployed on the outer circumference onthe forward end of the fitting stem 193, with a thickness and outerdiameter that are roughly equal to those of the fitting stem flange 194,and with an interval of 5 mm or so established between it and thefitting stem flange 194. The surface of this lens holding flange 196 towhich the double-sided adhesive pad 191 is bonded is made a sphericallyconcave lens holding surface 197 corresponding to the convex side lensface 1A of the lens 1. If the radius of curvature of the lens holdingsurface 197 is greater than the radius of curvature of the convex sidelens face 1A, only the center part of the lens holding surface 197 willmake contact with the convex side lens face 1A and the outer peripherythereof will not make contact, resulting in an unstable holding,whereas, conversely, if it is smaller, only the outer periphery of thelens holding surface 197 will make contact with the convex side lensface 1A and the center part thereof will not make contact, resulting ina comparatively stable holding and making it possible to prevent axisdislocation and the like, although if it is smaller by too much then thearea of contact, etc., will become small so that the holding becomesunstable. In other words, it is believed that the radius of curvature ofthe lens holding surface 197 should be set to a suitable size accordingto the radius of curvature of the convex side lens face 1A.

Here, when the lens 1 is a monofocal lens, in general the correspondingrange of power will be broad, wherefore, in order to be able to select abase curve defined by the degree of curvature in the curved surface ofthe convex side lens face which has a curve that is suitable to thepower, a number of base curves of different radiuses of curvature areestablished, and the curved surfaces having those established radiusesof curvature are termed “. . . curve” to specify them. In the case of acommon monofocal lens, for example, 12 types are prepared, from 0 curveto 11 curve. Now, a plurality of lens groups, wherein those havingsimilar curve constitute one group, are classified, with, for example, 0to 3 curve in a first lens group, 4 to 6 curve in a second lens group,and 7 to 11 curve in a third lens group. In this embodiment, a lensholder 19 having a lens holding surface 197 of a different radius ofcurvature is prepared for each lens group, with the holder used for thefirst lens group of 0 to 3 curve set at 4 curve, the holder used for thesecond lens group of 4 to 6 curve set at 7 curve, and the holder usedfor the third lens group of 7 to 11 curve set at 11 curve. In otherwords, the lens holder 19 is made in a number of types (three types)corresponding to the number of lens groups, so as to have a lens holdingsurface 197 that has a smaller radius of curvature than the convex sidelens face 1A of the lenses 1 belonging to each lens group (although thelens holder will have the same curve for lenses of 11 curve), so thatoutside contact is made with the convex side lens face 1A of the lens 1.Thus, when the curvature of the lens holding surface 197 of the lensholder 19 for each lens group is made deeper than the convex side lensface 1A of the lens 1, the lens can be held mainly by applying forces tothe outer circumferential edge of the lens holding surface 197, asdiagrammed in FIG. 19(b). However, only the curvature of the lensholding surface 197 differs, and the structure of the lens holders 19are otherwise exactly the same. When the difference between the radiusesof curvature of the convex side lens face 1A and the lens holdingsurface 197 is large, moreover, the adhesion between these two surfaceswill decline, wherefore it is preferable that difference be small.

In this embodiment, furthermore, the curve difference between the lensholding surface 197 and the convex side lens face 1A of the lens 1 isset to at least 1 curve, so that the lens holder 19 will always makecontact at the outside, but it is possible to cover cases where theseare the same curve or different by about 1 cover by the thickness andother properties of the double-sided adhesive pad 191.

As diagrammed in FIG. 19(b), furthermore, minute undulations 198 areformed in a radial pattern about the circumference of the lens holdingsurface 197 that constitutes a spherically concave surface, as notedearlier, in order to increase the adhesive binding force with thedouble-sided adhesive pad 191. The ridges and valleys of these minuteundulations 198 extend at more or less a constant angle in the radialdirection of the ring-shaped lens holding surface 197.

FIGS. 19(c) and 19(d) are diagrams that represent the cross-sectionalshape of the minute undulations 198 formed in the lens holding surface197 of this lens holder 19, and the way in which the pad 191 is bondedto those minute undulations 198, respectively. FIGS. 19(e) and 19(f) arediagrams that, by way of comparison, represent the cross-sectional shapeof minute undulations 199 in a conventional lens holder, and the way inwhich the pad 191 is bonded to those minute undulations 199,respectively. In either case, a cross-sectional shape is configuredwherein the ridges in the minute undulations 198 and 199 are ranged inthe circumferential direction of the lens holding surface 197.

In the conventional lens holder, as diagrammed in FIGS. 19(e) and 19(f),the cross-sectional shape of the minute undulations 199 is such thatthey form surfaces sloped on one side, with respect to the direction ofturning, so that the binding force with the pad 191 is maintained by abiting-in action toward the pad 191 caused by the turning. In otherwords, the wall surfaces 199 b on the sides toward the direction ofturning are configured by vertical surfaces, while the wall surfaces 199c on the opposite sides are configured as sloping surfaces, with theapexes 199 a of the ridges in the minute undulations 199 forming theboundaries therebetween.

However, when the minute undulations 199 having sloping surfaces on onlyone side in this manner are formed on the lens holding surface 197,although a binding force with the pad 191 is obtained due to thebiting-in action toward the pad 191, the adhesion with the pad 191 willdecline, as diagrammed in FIG. 19(f), so that it is not always possibleto obtain a high lens holding force. Also, because the sloped surfacesface in only one direction, when a pressing force acts between theminute undulations and the pad 191, there is a danger that unbalancedturning forces will be applied,when the pad thickness is thick, and thatthe pad 191 will be dislocated slightly in the direction of turning, sothat high-precision lens holding will be affected.

In contrast therewith, with this lens holder 19 (φ20), in addition tousing an adhesive pad that is on the thick side, the cross-sectionalshape of the undulations 198 in the lens holding surface 197 are made sothat the sloping sides face in both directions, as diagrammed in FIGS.19(c) and 19(d). In other words, the wall surfaces 198 b on the sidestoward the direction of turning and the wall surfaces 198 c on theopposite sides are configured as sloped surfaces having the same angleof inclination (45 degrees), with the apexes 198 a of the ridges in theundulations 198 forming the boundaries therebetween.

Accordingly, as diagrammed in FIG. 19(d), when the pad 191 is pressedagainst the minute undulations 198, the pad 191 will be bound evenly tothe sloped surfaces on both sides, and, due to the increase in the areaof contact, the moderate flexibility and deformability of the pad arewell utilized and the lens holding force can be increased. Also, becausethe pad 191 presses evenly against the sloped surfaces on both sides,which have the same angle of inclination, unbalanced turning forces arecancelled out and cease to be generated, wherefore such problems as theturning of the pad 191 getting shifted or lens holding precisiondeclining no longer occur.

By being able to increase the lens holding force, it is also possible tomake the diameter of the lens holding flange 196 smaller, the advantageswhereof are discussed below.

First, it then becomes possible to machine lenses of small diameter.Besides that, it is also then possible to reduce the number of types oflens holder prepared according to the lens curve (to weak power andstrong power, or with one or two types added therebetween). In otherwords, a plurality of types of lens holder 19 wherein the curvature ofthe lens holding surface 197 is altered in stages is prepared, so that,in general, these can be used according to the lens curve. In this case,because it is-not realistic to prepare lens holders according to alllens curves, provision is made so that a range of a number of types oflens curve (for strong and weak power or also for a power therebetween)are covered with one kind of lens holder.

FIG. 21 diagrams the relationship between the lens face 1A and the lensholding surface 197 of some particular curvature. When the curvature ofthe lens face 1A is larger than the curvature of the lens holdingsurface 197, the outer circumferential edge of the lens holding surface197 strikes the lens face 1A, and a depth difference F is formed betweenthe curve of the lens holding surface 197 and the curve of the lens face1A. When this depth difference F is large, the level of bonding betweenthe lens holding surface 197 and the lens face 1A declines. Therefore,provision is made so that a lens holder is prepared and can be selectedthat corresponds with the lens face 1A so that difference does notbecome large.

Now, when the outer diameter of the lens holding surface 197 (lensholding flange 196) is made smaller, even when the curve is the same,the depth difference F described above can be reduced, so that lenses ofmany curves can be handled. Accordingly, if a lens holder is used havinga smaller diameter, the range of lens curves that can be covered can bebroadened and, as a consequence, the number of types of lens holder canbe reduced.

In the example described in the foregoing, moreover, the cross-sectionalshape of the minute undulations 198 formed in the lens holding surface197 is made a ridge shape, but this cross-sectional shape may be made asmooth wavy shape, making the peaks of the ridges and the bottoms of thevalleys R-shaped. Also, in the example described in the foregoing, theridges and valleys in the minute undulations 198 are extendedcontinuously in the radial direction of the ring-shaped lens holdingsurface 197, but the minute undulations may also be scattered overeatentire lensholding surface 197.

FIG. 22 is a block diagram representing the electrical connectionrelationships, centered on a control device, in the lens machiningapparatus 10. Here, however, only the main essentials of theconfiguration are diagrammed. The control device comprises a servo motorcontroller 1001 and an I/O controller 1002. The two controllers 1001 and1002 perform data exchange data back and forth, and also exchange datawith a host computer (not shown). From a host computer that manages theoverall machining system, lens shape data (including moving radialinformation, convex side lens face shape, concave side lens face shape,lens thickness, and other diameter, etc.) and machining information andthe like are sent. Based on this shape data and machining information sosent, the controllers 1001 and 1002 subject lenses to necessarymachining.

The servo motor controller 1001 performs drive control on an X axisservo motor (lens turning motor 125), Y axis servo motor (cutting-inmotor 63), and Z axis servo motor (Z direction movement motor 331). TheI/O controller 1002 controls the driving of the cutter turning motor(tool motor) 133 for the cutter turning mechanism 13, a chamfering motor(end mill turning mechanism 14 and spindle motor 142), the lens chuckair cylinder 123, the measurement head turning actuator 155, a coolingair blower 1010, and the stylus opening and closing DC motor 170, viacontrollers and solenoid valves 1021 to 1026. When so doing, the signalsfrom various sensors are used in effecting control.

The I/O controller 1002 also uses a counter unit 1030 to count and fetchthe detection signals of the linear encoders 166 and 167 used for makingmeasurements. Further, in addition to effecting necessary displays on adisplay control unit 1100, the I/O controller 1002 fetches control inputsignals, and also sends necessary signals to a dust collector interfaceand conveyor robot interface.

Next, following the flowchart given in FIG. 23, the flow of controlperformed by the controllers 1001 and 1002 is described.

When the lens being machined 1 is set in the lens holding unit 12 and astart control input is made, first, measurement locus data sent from thehost computer are input (step S1). Next, the measurement head 16 islowered and positioned in the loaded position (step S2), the styluses161 and 162 are loaded relative to the lens 1 (step S3), the lensposition is measured (step S4), and those measurement data are sent tothe host computer (step S5).

When measurements for the entire circumference of the lens have beencompleted, the styluses 161 and 162 are unloaded from the lens 1 (stepS6), and the measurement head 16 is raised to the unloaded position(step S7). Next, machining locus data are input from the host computer(step S8), the motor (tool motor) 133 for the cutter turning mechanism13 is made to turn while the air blower is started (step S9), and thedust collector is operated (step S10).

Then, rough machining is executed by forced cutting edging) by turningthe cutter 131 a prescribed number of turns (step S11), next the turningspeed of the cutter turning motor 133 is changed (step S12), andfinishing machining is performed by forced cutting (edging) using thesame cutter 131 (step S13). At this time, if bevel edging is required,the bevel cutters Y1 and Y2 are selected and machining is performed.

When the finishing machining is complete, the cutter 131 is stopped(step S14), the spindle motor 142 is turned (step S15), and chamferingis performed by the end mill 141 on the edges of the convex side lensface and the concave side lens face (step S17). Prior to that, insteadof bevel edging, when a groove needs to be machined in the lenscircumferential surface, before doing the chamfering, the end mill 141is turned by the spindle motor 142, and a groove is cut (edged) in thelens edge surface (step S16). When chamfering is complete around theentire circumference, the spindle motor 142 and the air blower arestopped (step S18), the dust collector is stopped (step S19), and themachining of one lens is complete.

The rough machining and finishing machining described in the foregoingare done using the same cutter. That is, the flat cutting (edging)cutter H1 is selected for flat cutting (edging), the small bevel cutterY1 is selected for small bevels, and the large bevel cutter Y2 isselected for large bevels, and everything from rough machining tofinishing machining is performed with the same cutter. Accordingly,continuous machining with a single chucking is possible without movingthe process, whereupon machining time can be shortened and the equipmentmade smaller. Also, since it is not necessary to provide toolsseparately for rough machining and finishing machining, the space usedfor arranging the tools can be made smaller, and tool management is madeeasier.

Also, because the lens 1 is forcibly cut (edged) with the cutter 131,the cutting (edging) can be advanced while appropriately setting thecutting-in amount. That being so, the processes leading up to thefinished shape can be determined with machining conditions that areoptimal for the shape data. For example, it becomes possible to settargets freely, such as how many turns it will take to finish thecutting (edging), or how many seconds it will take to finish the cutting(edging), wherefore machining time can be shortened and machiningprecision enhanced.

Also, because the chamfering machining is performed with the R part ofthe tip of the end mill 141 of small diameter used for groove cutting(edging), compared to when a grindstone is used, there is littleinterference with other places, and small chamferings can be accuratelyfinished. In particular, because one end mill 141 is used for bothgroove machining and chamfering, the number of tools can be reduced andcontributions made to cost reduction, and groove machining andchamfering can be performed more or less continuously with one chucking,so that machining time can be shortened. Only one drive system is neededbecause the same tool is used for more than one purpose, wherefore theapparatus can be made smaller and costs reduced. And, because the numberof tools is not increased, tool management is also made easier.

Furthermore, in the case of this lens machining apparatus 10, themeasurement head 16 that performs lens measurements is deployed abovethe cutter 131 and end mill 141 serving as machining apparatuses, andmeasurements can be made on the lens 1 held by the lens holding unit 12by tilting the measurement head 16 forward only when needed, whereforethe measurement head 16 can be mounted on the machining apparatus 10without resorting to an unreasonable layout. Also, because themeasurement head 16 is mounted on the machining apparatus 10 such thatthe empty space above the cutter 131 and end mill 141 is effectivelyutilized, the area of the plan of the machining apparatus 10 need not beexpanded, and the machining apparatus 10 can be made smaller.Furthermore, because an entire series of processes from measurement tomachining can be done with the lens held in the lens holding unit 12,there is no longer any need at all to change the lens to move theprocess, nor is there any danger of machining precision declining due tolens changing, whereupon the lens shape can be accurately finished.

Next, various methods are described which are implemented in this lensmachining apparatus 10 in order to enhance machining precision andmachining efficiency, etc.

First, in this lens machining apparatus 10, a number of changeableparameters is used, including the turning speed of the cutter 131 (=toolturning speed), the turning speed of the lens holding shaft 121 whencutting (edging) the circumferential surface by the cutter 131 (=feedspeed), the number of revolutions of the lens 1 for the circumferentialsurface cutting (edging) machining (=number of cutting (edging) turns),the turning speed of the end mill 141 when cutting (edging),grooves orchamfering (=tool turning speed), and the turning speed of the lensholding shaft 121 at that time (feed speed). Provision is made so that,by setting those parameters according to the material of the lens 1(glass type of plastic here), the power (edge thickness=lens materialthickness), and whether the machining process is for finishing machiningor rough machining, etc., ideal machining conditions can be selected.

Provision is made so that, for example, by changing the parameters(cutter turning speed=tool turning speed, lens holding shaft turningspeed=feed speed, number of machining revolutions=number of cutting(edging) turns) according to the material (glass type) and power (edgethickness) of the lens 1, the machining load can be matched,irrespective of the material or power of the lens 1, lens size and lensshape (including bevel position) can be accurately and uniformlyfinished, and the machined places can be nicely finished. By selectingsuitable machining conditions, moreover, machining stress can bereduced, lens axis displacement reduced, tool life extended, andmachining time shortened.

Also, by changing the parameters (cutter turning speed=tool turningspeed, lens holding shaft turning speed=feed speed) according to whetherthe machining process is finishing machining or rough machining,finished surfaces can be made in good fashion, and the lens size andlens shape (including bevel position) finished accurately, whilemachining with the same cutter. By selecting appropriate machiningconditions, moreover, machining stress can be reduced, lens axisdisplacement decreased, and tool life extended.

Also, by changing the turning speed of the cutter 131 and/or the angularturning speed of the lens, in the same machining process, cutting(edging) speed can be made more uniform, wherefore machined surfaces canbe finished to uniform conditions.

Furthermore, even when performing groove cutting (edging) machining orchamfering machining by the end mill 141, by changing the parameters(end mill turning speed=tool turning speed, lens holding shaft turningspeed=feed speed) according to the material of the lens 1 (=type ofmaterial=glass type=type of plastic here), grooves and chamfered partscan be formed precisely, irrespective of the material of the lens 1. Byselecting suitable machining conditions, furthermore, tool life can beextended and machining time shortened.

FIG. 24 is a table giving actual examples of parameters (cutter turningspeed=tool turning speed, lens holding shaft turning speed=feed speed)determined according to different types of machining processes.

In FIG. 24, the uppermost column in the item columns in the left columnof the table is a column that specifies the lens type. The item at theupper level in this column labeled “HY1→machining speed→” is a levelwhich distinguishes the machining speed determined in correspondencewith the lens material. Specifically, there is a column to the right ofthe item column at this level wherein the numerals 1 and 2 are noted.The numeral 1 indicates that the lens material is a diethylene glycolbis-allyl carbonate material (where n_(d) is 1.50) or a polyurethanematerial (which is particularly to be preferred). The numeral 2indicates that the lens material is an epithio type resin. The columnsbelow the column for the numeral 1 are columns where “thick” and “thin”are noted, respectively, which are for classifying the lens materialthickness into two classes, for when that thickness is thick and whenthat thickness is thin, and imparting parameters thereto, respectively.

The numerals “00,” “02,” “05,” etc., noted in the columns below thecolumns in which “thick” and “thin” are noted are symbols (codes) thatrepresent speeds defined for each type of machining speed classified foreach machining type designated in the item column at the same level asthe level in which those numerals appear.

For example, for “circumferential surface rough machining feed speed,” acode of “02” indicates that the speed is “1 turn in 22 seconds,” a codeof “03” that the speed is “1 turn in 30 seconds,” and a code of “04”that the speed is “1 turn in 38 seconds,” respectively.

Similarly, for “circumferential surface rough machining tool turningspeed,” a code of “05” indicates a speed of “9600 rpm,” and a code of“04” a speed of “8000 rpm,” respectively.

For “circumferential surface finishing machining feed speed,” a code of“05” indicates a speed of “1 turn in 46 seconds.” And for“circumferential surface finishing machining tool turning speed,” a codeof “00” indicates a speed of “2000 rpm,” and a code of “02” indicates aspeed of “3800 rpm,” respectively.

For “groove machining feed speed,” a code of “02” indicates a speed of“1 turn in 22 seconds,” and a code of “04” a speed of “1 turn in 38seconds” (the same as for “circumferential surface rough machining feedspeed”), while for “groove machining tool turning speed,” a code of “01”indicates a speed of “28,000 rpm,” and a code of “00” indicates a speedof “20,000 rpm,” respectively.

For “chamfering feed speed,” a code of “02” indicates a speed of “1 turnin 22 seconds,” and a code of “04” indicates a speed of “1 time in 38seconds” (the same as for “circumferential surface rough machining feedspeed”), while for “chamfering took turning speed,” a code of “00”indicates a speed of “20,000 rpm,” and a code of “01” a speed of “28,000rpm,” respectively.

In the example given in the table described above, for a materialdesignated by the numeral 1, machining is performed under the samemachining conditions even when the material thickness differs, but for amaterial designated by the numeral 2, because the material strength ismore brittle than that designated by the numeral 1, provision is madefor performing machining slowly over a longer period of time, and themachining conditions are made slightly different depending on thematerial thickness.

By effecting such control as this, the machining load is balanced, andlens size and lens shape (inclusive of the bevel position) are finishedaccurately and uniformly, irrespective of the material or power of thelens 1. While that is done, it is also important, in order to neatlyfinish the machined sites, to make the feed speed (lens shaft turningspeed) and tool turning speed suitable, as described in the foregoing,and to set the number of machining revolutions (number of cutting(edging) turns) so as to be suitable.

FIG. 25 is a graph that plots the relationship between maximum lensmaterial thickness and number of cutting (edging) turns (number ofmachining revolutions) for rough machining when machining of aprescribed precision is possible without shaft displacement. In thisfigure, the number of cutting (edging) turns (number of machiningrevolutions)—is plotted on the vertical axis Y and the maximum lensmaterial thickness (unit=mm) on the horizontal axis X.

Maximum material thickness here refers to the maximum edge thickness atthe outer diameter of the lens in the case of a minus lens, and themaximum material thickness in the lens frame shape in the case of a pluslens. In such cases, moreover, the lens holding shaft turning speed(feed speed) is based on a standard of 1 turn in 22 seconds for roughwork, for example, under conditions that the circumference speed isconstant and that no shaft displacement occurs. The number of machiningrevolutions is equal to the number of revolutions required for thecutter to cut in with a spiral locus on the lens plus a final 1 turn(constant) for machining to adjust the shape for which finishingmachining portions are left remaining uniformly.

In FIG. 25, the straight line 1 assumes a polyurethane lens material(having a refractive index n_(d) of 1.56 to 1.74 or so, for example)that exhibits intermediate cutting (edging) properties, for the material(type of material) of the lens.

From this graph, a relationship of Y=0.8X−3.1+1 (constant) is indicated(rounded off) in the polyurethane resin type lens, in cases where themaximum material thickness exceeds 5.9 mm. Here, a relationship ofY=0.87X−3.1+1 (constant) can be used in an epithio type resin lenshaving different material properties, for example. Also, in cases wherethe maximum material thickness is 5.9 mm or less, the value of Y becomesuniformly 1 without being dependent on X.

Furthermore, in the rough machining, regarding the total number ofcutting (edging ) turns except the final 1 turn, the cutting-in locuswhen doing cutting (edging) is a spiral, as will be describedsubsequently (with reference to FIG. 28(a), for example).

By using the graph, etc., described in the foregoing, the number ofmachining revolutions (number of cutting (edging) turns) can be set to asuitable value according to the lens material thickness.

With this lens machining apparatus 10, moreover, computation functionssuch as are described below are provided so that lens position datanecessary when performing bevel edging can be accurately obtained. Suchis described using FIG. 26.

Ordinarily, in order to obtain position data on the lens surfaces 1A and1B, the styluses 161 and 162 are made to trace over the lens faces 1Aand 1B according to the lens shape data, and the positions 1 e and 1 fon the lens faces are measured by detecting the positions of thestyluses 161 and 162 at each point on that locus. The positions of thestyluses 161 and 162 in this case are on an extended line ST in thedirection of the lens holding shaft at the apex of the bevel 1 a formedwhen the lens 1 was bevel-edged.

However, when bevel edging is performed simply on the basis of theposition data (coordinate data at 1 e and 1 f) found in this way, aproblem arises in that it is not possible to accurately finish theposition of the bevel 1 a. That is, although it is desired to preciselyfind the position of the bevel 1 a in the lens circumferential surfacein the machined condition, based on the edges 1 c and 1 d on both sidesof the lens circumferential surface, the actual bevel edging is donebased on data measured at the positions 1 e and 1 f on the outercircumference side, removed from the positions of the two side edges 1 cand 1 d by the measure of the bevel height SH. Accordingly, the bevel 1a cannot be finished with high precision.

One conceivable solution to this would be to cause the styluses 161 and162 to trace at positions that are the positions defined beforehand bythe lens shape data from which the bevel height SH has been subtracted,thereby measure beforehand the positions of the edges 1 c and 1 d at thetwo edges of the lens circumferential surface in the machined condition,and perform bevel edging based on those position data.

When that is done, however, it is necessary to cause the styluses 161and 162 to trace closer in toward the center of the lens than thepositions defined by the lens shape data, thus making it necessary toprepare data beforehand for making the styluses 161 and 162 do theirtracing that are separate from the lens shape data. Also, in order tocause tracing closer in toward the center of the lens, there is a dangerthat the contact marks from the styluses 161 and 162 will remain withinthe range of the lens faces 1A and 1B that may possibly be finally used.

Thereupon, in this lens machining apparatus 10, provision is made sothat the coordinate values for the points 1 c and 1 d are calculatedbased on measured coordinate data for the points 1 e and 1 f, and ondesign data for the lens 1 provided separately. Here, by design data forthe lens 1 is meant lens property data (refractive index, abbe number,specific gravity, etc.), prescription related data (lens power, cylinderaxis, addition (Add), prism, base direction, decentration, outerdiameter, distance PD, near PD, lens thickness, VR value (CR value+VCvalue)), frame data (shape, DBL, FPD, frame curve, and frame curve,etc.), frame forward tilt, type of bevel, and other machining processdesignating data. In the design data for the lens 1 in this case arecontained moving radial data, convex side lens face shape data, concaveside lens face shape data, lens thickness data, and outer diameter data,wherein are also contained a limited number of coordinate data (ρi, θi,Zi) that define the shapes of the convex side lens face 1A and theconcave side lens face 1B, and it is possible to extract the coordinatesfor any point on either the convex side lens face 1A or the concave sidelens face 1B even in the case of a aspherical lens. Accordingly, byusing these design data together with the actually measured datameasured at trace points on the extended line SH in the lens holdingshaft direction for the bevel apex, the positions of the points 1 c and1 d can be precisely calculated. Then, by using those coordinate datafor the points 1 c and 1 d, the bevel 1 a can be precisely machined.Provision is made so that the design data are made available from lensdesign program data in the host computer.

In this lens machining apparatus 10, furthermore, the measurement head16 for measuring lens shapes and lens positions is made so that, asnecessary, it can make an approach from a holding location toward thelens 1 held by the lens holding unit 12. Therefore, in addition tomeasurements prior to machining, lens shapes and lens positions can alsobe measured during machining, in special cases. An example of a casewherein measurement is implemented during machining is described next.

An example of machining processing is diagrammed in FIG. 27, withmachining processing in an ordinary case diagrammed at (a), andmachining processing in a special case diagrammed at (b). In themachining processing diagrammed in FIG. 27(a), lens measurement isperformed at the stage of an unmachined lens, while in the machiningprocessing diagrammed in FIG. 27(b), lens measurement is performed at astage midway along in rough machining. In this lens machining apparatus10, provision is made so that machining is implemented after selectingeither the machining processing in (a) or the machining in (b),according to the lens material (glass type) and power (edge thickness).The reason for providing the special machining processing diagrammed inFIG. 27(b) as a selection choice is that there are cases wheredifferences arise in the values of lens measurements made at theunmachined lens stage and a stage midway along in rough machining, suchthat, when the ordinary machining processing given in FIG. 27(a) is madethe standard for all cases, there will be times when it will not bepossible to accurately finish the bevel position in final finishingmachining.

In the case of the ordinary machining processing diagrammed in FIG.27(a), lens measurements are conducted at the outset. Rough machining isthen implemented, followed next by finishing machining, and followedlast of all by chamfering to yield the lens in its final shape. Therough machining is performed up to a point that leaves material for thefinishing cutting (edging). The last of the cutting (edging) material isremoved in the finishing machining and the final dimensions arefinished.

In the case of the special machining processing diagrammed in FIG.27(b), on the other hand, primary rough machining is first implemented,after which lens measurements are made. As diagrammed in FIGS. 28(a) and28(b), primary rough machining is performed until dimensions are reachedwhich leave a measurable width SK relative to the finished dimensions.In the rough machining employed in the ordinary machining processing,only the cutting (edging) material remaining for finishing is leftremaining, but it is difficult to have the styluses 161 and 162 maketraces within the range of cutting (edging) material no more extensivethan that. Thereupon, in this machining processing, by going ahead withthe primary rough machining, machining is performed up to a point wherea width that is in a measurable range (1.5 to 1.8 mm or so, for example)is left remaining.

As to why this is done, as stated earlier, when an unmachined lens issubjected all at once to rough machining that leaves only enough cutting(edging) material for the finishing, there are cases where, with certainspecial lenses, the lens holding condition changes. That is, dependingon the lens holding condition, at the unmachined lens stage, the portionof material that is to be removed in the rough machining thereafterexhibits a reinforcing effect and elicits holding balance, arrestingholding deformation before it appears on the surface. When that portionof lens material is removed in the rough machining, the reinforcingeffect disappears, and, in some cases, holding deformation appears onthe surface. Accordingly, in such cases, even if lens measurement valuesare found at the unmachined lens stage, those initial lens position datawill change at a stage after the rough machining has actually been done,and reliability will decline. Examples are bifocal lenses wherein thereis a segment, and lenses having thick edge thickness.

Thus, after implementing lens measurement at this stage at which primaryrough machining has been performed, and obtaining lens informationcontaining the edge thickness in a condition wherein the effects of lensholding deformations are not received, by then performing secondaryrough machining, and removing cutting (edging) material up to the stagewhere the cutting (edging) material for finishing is left remaining, andthereafter implementing finishing machining, in the same manner as inmachining processing in ordinary cases, and implementing chamferingmachining last of all, the lens is obtained in its final shape.

Thus, by implementing lens measurement at a stage midway along in therough machining, highly reliable lens measurement values can beobtained, wherefore, by performing subsequent finishing machining usingthose lens measurement values, the lens shape and bevel shape can befinished accurately. In this embodiment, an example is cited wherein acutter is used as a tool, but a grindstone may be used instead of acutter if the same degree of control can be maintained as with a cutter.

INDUSTRIAL APPLICABILITY

In terms of industrial usefulness, with the present invention, asdescribed in the foregoing, it becomes possible to provide a lensmachining apparatus and lens machining method wherewith, when a lensbeing machined for use in spectacles is held by the center of the lens,the circumferential surface of the held lens being machined is edgedaway with a revolving machining tool for use in circumferential surfacemachining and the lens being machined is also made to revolve about thecenter of the lens, and thereby the circumferential surface is edgedaway about the entire circumference of the lens being machined, andthereby a lens having a prescribed circumferential edge shape ismachined, provision is made so that edging machining on the lenscircumferential surface, inclusive of bevel edging, groove machining toform a grove in the lens circumferential surface, and chamferingmachining to chamfer the edges where the lens circumferential surfaceand lens faces intersect are performed, while holding the lens beingmachined by the lens holding unit, maintaining the condition of holdingby that lens holding unit unchanged, whereby not only can everythingrequired in eyeglass lens machining, from measurement to various typesof machining, be performed with a single chucking operation, buthigh-precision machining can also be realized.

What is claimed is:
 1. A spectacle lens machining apparatus, comprising:a lens holding unit provided with a lens holding shaft which is aturnable shaft and which has a mechanism of holding a spectacle lensbeing machined at a center of the lens in such a manner that a directionof said shaft intersects a lens optical surface, and also provided witha turn driving mechanism which drives said lens holding shaft so as toturn according to a predetermined machining command information, therebyrotating said spectacle lens about the center of the spectacle lens tomove a machined position of a circumferential edge of the spectaclelens; a lens machining mechanism provided with a revolving machiningtool which edges the circumferential edge of said spectacle lens beingmachined that is held by said lens holding unit according to thepredetermined machining command information, to machine the spectaclelens to a predetermined spectacle frame shape; a ball end mill which isprovided to machine a groove in an end surface of the circumferentialedge of the spectacle lens being machined that has been machined to thepredetermined spectacle frame shape by said lens machining mechanism andto chamfer edges where the end surface of the circumferential edge ofsaid spectacle lens being machined and the optical surface of this lensintersect, according to a predetermined machining command information;and a control information processing apparatus which has a function ofsending necessary information including the predetermined machiningcommand information to said lens holding unit, said lens machiningmechanism, and said ball end mill, to control their operations.
 2. Thespectacle lens machining apparatus according to claim 1, wherein: therevolving machining tool of said lens machining mechanism is a cutterprovided with a revolving cutting blade; and said control informationprocessing apparatus has a function of, in machining said spectacle lensbeing machined to the predetermined spectacle frame shape by cutting thecircumferential edge thereof, sending different machining commandinformation when necessary corresponding to a rough machining stage anda finishing machining stage respectively, into which this machiningprocess is divided.
 3. The spectacle lens machining apparatus accordingto claim 2, wherein the revolving machining tool of said lens machiningmechanism has a flat cutting cutter which flat-cuts the end surface ofthe circumferential edge of said spectacle lens being machined and abevel cutting cutter which bevel-cuts the end surface of thecircumferential edge of said spectacle lens being machined, and iscapable of using either one selected from these cutters according to thepredetermined machining command information.
 4. The spectacle lensmachining apparatus according to claim 1, further comprising: a lensshape measurement apparatus including: a position measurement apparatuswhich measures coordinates of a predetermined position of the lensoptical surface of said spectacle lens being machined that is held bysaid lens holding unit; and a measurement information processingapparatus, which sends control command information to said lens holdingunit and a moving mechanism for said lens holding unit, controls aposition of said spectacle lens being machined relative to said positionmeasurement apparatus to measure coordinates of each position of theoptical surface of said spectacle lens being machined, and finds shapeinformation necessary for machining said spectacle lens being machinedbased on information on this measurement.
 5. A spectacle lens machiningmethod of subjecting a spectacle lens being machined rough machining andfinishing beveling based on pre-obtained data on a spectacle frame shapewhich is an object of machining, thereby machining said spectacle lensbeing machined to a predetermined spectacle frame shape, using aspectacle lens machining apparatus which includes: a lens holding unitprovided with a lens holding shaft which is a turnable shaft and whichhas a mechanism of holding the spectacle lens being machined at a centerof the lens in such a manner that a direction of said shaft intersects alens optical surface, and also provided with a turn driving mechanismwhich drives said lens holding shaft so as to turn according to apredetermined machining command information, thereby rotating said lensabout the center of the spectacle lens to move a machined position of acircumferential edge of the spectacle lens; a lens machining mechanismprovided with a revolving machining tool which edges the circumferentialedge of said spectacle lens being machined that is held by said lensholding unit according to the predetermined machining commandinformation, to machine the spectacle lens to the predeterminedspectacle frame shape; and a control information processing apparatuswhich has a function of sending necessary information including thepredetermined machining command information to said lens holding unitand said lens machining mechanism to control their operations, wherein asame beveling tool is used for a series of cutting machining from saidrough machining to said finishing beveling; said rough machining processis performed being divided into a primary rough machining process and asecondary rough machining process; said primary rough machining processis a process of cutting in a spiral locus relative to the end surface ofthe circumferential edge of said spectacle lens being machined, therebymachining the spectacle lens being machined to a substantially equalshape to said shape of the machining object; said secondary roughmachining process is a process of machining the spectacle lens beingmachined that has been subjected to said primary rough machining untilonly a portion to be cut away by the subsequent process of the finishingbeveling is left equally along an entire lens periphery at the endsurface of the circumferential edge of the spectacle lens beingmachined; and said finishing beveling process is a process of forming afinal beveling surface on the end surface of the circumferential edge ofsaid spectacle lens being machined.
 6. A spectacle lens machining methodof subjecting a spectacle lens being machined to rough machining andfinishing beveling based on pre-obtained data on a spectacle frame shapewhich is an object of machining, thereby machining said spectacle lensbeing machined to a predetermined spectacle frame shape, using aspectacle lens machining apparatus which includes: a lens holding unitprovided with a lens holding shaft which is a turnable shaft and whichhas a mechanism of holding the spectacle lens being machined at a centerof the lens in such a manner that a direction of said shaft intersects alens optical surface, and also provided with a turn driving mechanismwhich drives said lens holding shaft so as to turn according to apredetermined machining command information, thereby rotating said lensabout the center of the spectacle lens to move a machined position of acircumferential edge of the spectacle lens; a lens machining mechanismprovided with a revolving machining tool which edges the circumferentialedge of said spectacle lens being machined that is held by said lensholding unit according to predetermined machining command information,to machine the spectacle lens to a predetermined spectacle frame shape;a control information processing apparatus which has a function ofsending necessary information including the predetermined machiningcommand information to said lens holding unit and said lens machiningmechanism to control their operations; and a lens shape measurementapparatus including: a position measurement apparatus which measurescoordinates of a predetermined position of the optical surface of saidspectacle lens being machined that is held by said lens holding unit;and a measurement information processing apparatus which sends controlcommand information to said lens holding unit, controls a position ofsaid spectacle lens being machined relative to said position measurementapparatus to measure coordinates of each position of the optical surfaceof said spectacle lens being machined, and finds shape informationnecessary for machining said spectacle lens being machined based oninformation on this measurement, wherein at a middle stage of said roughmachining, said lens shape measurement apparatus measures shape at eachposition along a locus of a designed machined shape of the spectaclelens being machined that has been subjected to the rough machining,information on lens shape including an edge thickness at each positionalong the locus of said designed machined shape is tentatively obtained,and the bevel finishing using this shape information is performed.